Oxidative Addition of (Hetero)aryl (Pseudo)halides at Palladium(0): Origin and Significance of Divergent Mechanisms.

Two limiting mechanisms are possible for oxidative addition of (hetero)aryl (pseudo)halides at Pd(0): a 3-centered concerted and a nucleophilic displacement mechanism. Until now, there has been little understanding about when each mechanism is relevant. Prior investigations to distinguish between these pathways were limited to a few specific combinations of the substrate and ligand. Here, we computationally evaluated over 180 transition structures for oxidative addition in order to determine mechanistic trends based on substrate, ligand(s), and coordination number. Natural abundance 13C kinetic isotope effects provide experimental results consistent with computational predictions. Key findings include that (1) differences in highest occupied molecular orbital (HOMO) symmetries dictate that, although 12e- PdL is strongly biased toward a 3-centered concerted mechanism, 14e- PdL2 often prefers a nucleophilic displacement mechanism; (2) ligand electronics and sterics, including ligand bite angle, influence the preferred mechanism of the reaction at PdL2; (3) phenyl triflate always reacts through a displacement mechanism regardless of the catalyst structure due to the stability of a triflate anion and the inability of oxygen to effectively donate electron density to Pd; and (4) the high reactivity of C-X bonds adjacent to nitrogen in pyridine substrates relates to stereoelectronic stabilization of a nucleophilic displacement transition state. This work has implications for controlling rate and selectivity in catalytic couplings, and we demonstrate application of the mechanistic insight toward chemodivergent cross-couplings of bromochloroheteroarenes.

Highly Regioselective Copper-Catalyzed Transfer Hydrodeuteration of Unactivated Terminal Alkenes.

Catalytic transfer hydrodeuteration of unactivated alkenes is challenging because of the requirement that chemically similar hydrogen and deuterium undergo selective insertion across a π-bond. We now report a highly regioselective catalytic transfer hydrodeuteration of unactivated terminal alkenes across a variety of heteroatom- or heterocycle-containing substrates. The base-metal-catalyzed reaction is also demonstrated on two complex natural products. Reaction studies indicate modular conditions that can also be extended to perform either an alkene transfer hydrogenation or transfer deuteration.

Copper-Catalyzed Transfer Hydrodeuteration of Aryl Alkenes with Quantitative Isotopomer Purity Analysis by Molecular Rotational Resonance Spectroscopy.

A copper-catalyzed alkene transfer hydrodeuteration reaction that selectively incorporates one hydrogen and one deuterium atom across an aryl alkene is described. The transfer hydrodeuteration protocol is selective across a variety of internal and terminal alkenes and is also demonstrated on an alkene-containing complex natural product analog. Beyond using 1H, 2H, and 13C NMR analysis to measure reaction selectivity, six transfer hydrodeuteration products were analyzed by molecular rotational resonance (MRR) spectroscopy. The application of MRR spectroscopy to the analysis of isotopic impurities in deuteration chemistry is further explored through a measurement methodology that is compatible with high-throughput sample analysis. In the first step, the MRR spectroscopy signatures of all isotopic variants accessible in the reaction chemistry are analyzed using a broadband chirped-pulse Fourier transform microwave spectrometer. With the signatures in hand, measurement scripts are created to quantitatively analyze the sample composition using a commercial cavity enhanced MRR spectrometer. The sample consumption is below 10 mg with analysis times on the order of 10 min using this instrument-both representing order-of-magnitude reduction compared to broadband MRR spectroscopy. To date, these measurements represent the most precise spectroscopic determination of selectivity in a transfer hydrodeuteration reaction and confirm that product regioselectivity ratios of >140:1 are achievable under this mild protocol.

Students' perceptions and experiences of an online well-being programme: a phenomenological study protocol.

BACKGROUND: The pandemic has ensued challenges across all sections of the human population such as livelihood and educational changes, which involve the abrupt shift to online learning, immensely affecting the students' well-being. Negative health consequences of e-learning among students stem from the increased demand for new technological skills, productivity, information overload and restriction of students to spend time with their peers. OBJECTIVE: To explore the experiences of the students from the University of Santo Tomas-College of Rehabilitation Sciences (UST-CRS) who participated in the online well-being programme. METHODOLOGY: A phenomenological design will be used to determine the participants' perceptions and experiences. Purposive sampling will be used to recruit 8-10 undergraduate students from UST-CRS ages 18-22 years, who participated in the well-being programme, and completed the study's quantitative counterpart. Semistructured, in-depth questions will be used to conduct a focus group discussion. The transcripts will be analysed using thematic analysis via the NVivo V.12 software. ETHICS AND DISSEMINATION: The study protocol is approved by the UST-CRS Ethical Review Committee (Protocol Number: SI-2022-034 (V.4)). It will be implemented in accordance with the Declaration of Helsinki and the National Ethical Guidelines for Health and Health-Related Research, and Data Privacy Act. Findings will be published in accredited journals and presented in related scientific fora. REGISTRATION ID: PHRR230214-005419; Philippine Health Research Registry.

Copper-Catalyzed Formal Transfer Hydrogenation/Deuteration of Aryl Alkynes.

A copper-catalyzed reduction of alkynes to alkanes and deuterated alkanes is described under transfer hydrogenation and transfer deuteration conditions. Commercially available alcohols and silanes are used interchangeably with their deuterated analogues as the hydrogen or deuterium sources. Transfer deuteration of terminal and internal aryl alkynes occurs with high levels of deuterium incorporation. Alkyne-containing complex natural product analogues undergo transfer hydrogenation and transfer deuteration selectively, in high yield. Mechanistic experiments support the reaction occurring through a cis-alkene intermediate and demonstrate the possibility for a regioselective alkyne transfer hydrodeuteration reaction.

Psychometric Characteristics of Spanish Monosyllabic, Bisyllabic, and Trisyllabic Words for Use in Word-Recognition Protocols.

BACKGROUND: English materials for speech audiometry are well established. In Spanish, speech-recognition materials are not standardized with monosyllables, bisyllables, and trisyllables used in word-recognition protocols. PURPOSE: This study aimed to establish the psychometric characteristics of common Spanish monosyllabic, bisyllabic, and trisyllabic words for potential use in word-recognition procedures. RESEARCH DESIGN: Prospective descriptive study. STUDY SAMPLE: Eighteen adult Puerto Ricans (M = 25.6 years) with normal hearing [M = 7.8-dB hearing level (HL) pure-tone average] were recruited for two experiments. DATA COLLECTION AND ANALYSES: A digital recording of 575 Spanish words was created (139 monosyllables, 359 bisyllables, and 77 trisyllables), incorporating materials from a variety of Spanish word-recognition lists. Experiment 1 (n = 6) used 25 randomly selected words from each of the three syllabic categories to estimate the presentation level ranges needed to obtain recognition performances over the 10 to 90% range. In Experiment 2 (n = 12) the 575 words were presented over five 1-hour sessions using presentation levels from 0- to 30-dB HL in 5-dB steps (monosyllables), 0- to 25-dB HL in 5-dB steps (bisyllables), and -3- to 17-dB HL in 4-dB steps (trisyllables). The presentation order of both the words and the presentation levels were randomized for each listener. The functions for each listener and each word were fit with polynomial equations from which the 50% points and slopes at the 50% point were calculated. RESULTS: The mean 50% points and slopes at 50% were 8.9-dB HL, 4.0%/dB (monosyllables), 6.9-dB HL, 5.1%/dB (bisyllables), and 1.4-dB HL, 6.3%/dB (trisyllables). The Kruskal-Wallis test with Mann-Whitney U post-hoc analysis indicated that the mean 50% points and slopes at the 50% points of the individual word functions were significantly different among the syllabic categories. Although significant differences were observed among the syllabic categories, substantial overlap was noted in the individual word functions, indicating that the psychometric characteristics of the words were not dictated exclusively by the syllabic number. Influences associated with word difficulty, word familiarity, singular and plural form words, phonetic stress patterns, and gender word patterns also were evaluated. CONCLUSION: The main finding was the direct relation between the number of syllables in a word and word-recognition performance. In general, words with more syllables were more easily recognized; there were, however, exceptions. The current data from young adults with normal hearing established the psychometric characteristics of the 575 Spanish words on which the formulation of word lists for both threshold and suprathreshold measures of word-recognition abilities in quiet and in noise and other word-recognition protocols can be based.

Cancer of the larynx in Puerto Rico.

INTRODUCTION: Cancer of the larynx is the fourteenth most common cancer in the world. The purpose of this cross-sectional study is to examine the characteristics of laryngeal cancer in Puerto Rico. The study evaluates whether this type of cancer is increasing, to what degree gender differences occur; and describe common types of medical treatment. METHOD: Information on cases of laryngeal cancer for the period of 1997 to 2002 was collected at the Puerto Rico Central Cancer Registry, Department of Health. The incidence of laryngeal cancer in Puerto Rico during the study period was estimated. Sex differences in case-fatality rate and other variables were analyzed. Medical treatments for laryngeal cancer were also analyzed. RESULTS: The study revealed that the average incidence of laryngeal cancer in Puerto Rico was 3.8 x 100,000 from 1997-1998 and 3.5 x 100,000 from 2001-2002 (-1.07 APC). Of all the cases (n = 848) of laryngeal cancer reviewed, 88% were male. Females were more likely to be diagnosed before age 50 than males (p = 0.02). In this study, women had twice the probability of being alive at the end of the study period (OR = 1.97; CI: 1.14-3.45). The two most frequent types of single treatments for laryngeal cancer were radiation (39%) and surgery (33%). CONCLUSIONS: Cases oflaryngeal cancer are decreasing in Puerto Rico. Significant differences by sex were observed, especially the stage of the disease at the time of diagnosis. Future studies on medical treatment modalities that better preserve vocal function concurrently with voice therapy are recommended.

Voice disorders in the Metropolitan Area of San Juan, Puerto Rico: profiles of occupational groups.

OBJECTIVES/HYPOTHESIS: Approximately 28,000,000 workers in the United States experience voice problems everyday. In general, voice problems are very common, but they are more frequent among certain occupational groups. STUDY DESIGN: Descriptive cross-sectional study. METHOD: We analyzed 129 available records of voice-disordered cases reported during the period of 2000-2005 from the Corporación del Fondo del Seguro del Estado in the Metropolitan Areas of Puerto Rico of Bayamón, San Juan, and Carolina. The following variables were studied: sex, age, occupation, possible job hazards, diagnosis, and type of treatment. Measures of central tendency, including percentage frequencies, were used. RESULTS: The findings revealed that 81% of all the cases of voice disorders available during the study period were females. The average age at diagnosis for different voice disorders was 42 years (± 10 years). Vocal problems were reported with a higher frequency by teachers at the elementary and high school levels (72%). The most common complaints were job-related voice overuse (30%) and excessive dust at the workplace. The most frequent medical diagnoses related to voice disorders were rhynopharyngitis (27%), several types of laryngitis (21%), and laryngopharyngitis (10%). The most frequent treatment modality for laryngeal disease and voice problems was the prescription of medication. CONCLUSIONS: The most relevant factor of voice disorders for professional voice users is the vocal overload during their job. It is advisable to implement voice disorder-prevention programs for teachers because of the high rate of vocal dysfunction among these professionals.